This invention relates to a silver halide color photographic material containing a novel photographic, compound that is capable of timed release of photographically useful groups. More particularly, this invention relates to a silver halide color photographic material having smooth gradation from the high- to the low-exposure range.
Various methods are known as means for achieving imagewise release of photographically useful groups by making use of compounds that are to be put to photographic use. See, for example, U.S. Pat. No. 8,148,062 to Whitmore et al. and U.S. Pat. No. 3,227,554 to Bart et al., which disclose a method of reacting a photographic coupler with an oxidized color developer so that a development inhibitor or a dye is released from the coupling site of the coupler. This prior art method and the compounds used are classified as a technique for causing photographically useful groups to be directly released from those compounds. However, this direct release approach is not suitable for use in certain eases that need various adjustments; for instance, the release time of photographically useful groups may have to be accelerated or retarded in consideration of various reactions that are caused by other materials in the photographic material; alternatively, photographically useful groups may have to be shifted by a certain distance in order to insure that they will exhibit their intended effects in a predetermined constituent layer or position in the photographic material. In these cases, considerable difficulty is involved in achieving the necessary adjustments by the direct release method. If one wants to solve this problem by the prior art technology, it is necessary not only to select appropriate components that release photographically useful groups but also review means for coupling photographically useful groups to the selected components. In addition, the photographically useful groups per se must be carefully selected. Thus, it is essential to make an extensive review from a broad range of viewpoints but such adjustments are in conflict with the objects or effects that are desirably achieved by the aforementioned components or photographically useful groups. As a result, the degree of freedom in selecting the appropriate components is reduced rather than increased in connection with the intended objects.
A contrastive approach, or a method of releasing photographically useful groups indirectly, is described in Unexamined Published Japanese Patent Application No. 145135/1979, U.S. Pat. No. 4,284,962 and European Patent No. 299,726. According to these patents, the first stage of cleavage is caused by reaction with the oxidation product of a color developing agent and, thereafter, the second stage of cleavage is effected by performing an intramolecular nucleophilic substitution reaction, so that adjustment can be made over a broad range in order to control many parameters including time or distance adjustments of the effects that are to be achieved by the photographically useful groups which are the final end products.
The photographic couplers described specifically in the patents listed above must satisfy the essential requirement that nucleophilic groups be directly coupled to the coupler component but this offers the disadvantage of limiting the degree of freedom in selecting the coupler component and the nucleophilic group. Under the circumstances, it often becomes necessary to use coupler components that are low in coupling performance or the coupler components used may decompose during storage to deteriorate the silver halide photographic material in which they are incorporated.
A method for eliminating these defects has been proposed in Unexamined Published Japanese Patent Application No. 114946/1981; however, the proposal is still unsatisfactory in terms of coupling performance and the effective range of photographically useful materials and there has remained much room for extending the latitude. Common color negative films, as they are loaded in a camera, are used to take pictures of various objects under various conditions; hence, in order to insure that image can be recorded or more image information can be recorded even if the amount of exposure is somewhat deviated from the proper range, it is necessary to design films that have greater latitude. To meet this need, two or more kinds of silver halide emulsions that are sensitive to the same color but in different degrees are used so that image information can be recorded from the high- to low-exposure range. In this case, it is required that the characteristic curve (plotting image density D vs -log E; E is the amount of exposure) be smooth but if the DIR compounds proposed in Unexamined Published Japanese Patent Application No. 114946/1981 are used, it has been difficult to achieve a smooth characteristic curve without lowering the sensitivity in the low-exposure area.